Purification and physico-chemical characterization of the three functionally recognized middle components of the shark complement system. Elucidation of the conditions of intermediate complex formation. Establishing of compatibilities and incompatibilities with respective mammalian complement components. Cln preparation on large scale. Elucidation of the immunochemical relationship between C4I, C4I precursor and Cln. Studies regarding the C4I generating system. Comparison of the kinetics of C4I, Cln and Cl inactivation by mammalian (human) and shark Cl INH. Search for the antigens reactive with natural shark antibodies and further investigations of their functional role for heterologous cells (PMNs, macrophages, erythrocytes). BIBLIOGRAPHIC REFERENCES: Jensen, J.A. and Esquenazi, V. Chemotactic Stimulation by Cell Surface Immune Reactions. Nature 256, 213 1975. Jensen, J.A., Esquenazi, V., Williams, D., and Cirocco, R. Chemotaxis of Leukocytes Induced by Cell Surface Immune Reactions. Future Trends in Inflammation, In Agents and Actions, Birkhauser Verlag, Basel, 1975.